A chuck, which draws a work against the chuck-face, is disclosed in U.S. Pat. No. 3,460,849 or in German Patent laid open No. 2 639 818. The chuck of this type, as the conventional chuck, a jaw is also drawn with a part of the chuck body, being guided along a guide slot radially disposed at the chuck body and restricted in axial and radial movement, when a work piece is drawn.
A general construction of these chucks, for instance, a chuck disclosed in U.S. Pat. No. 3,460,849, is shown in FIG. 16.
As shown in FIG. 16, a chuck body 60 generally comprises a first or outer body part 61 having an inner rear face for engaging the spindle (not shown) of a lathe. The first body part 61 is generally annular in shape and an inner body 62 is slidably mounted in concentric relation with respect thereto for slidable movement in an axial direction between a retracted position wherein an external shoulder defined in said second body part engages a radially extending internal shoulder on the first body 61.
There is provided a T-slot 68, 70 in a plug 67 connected to a draw bar 66 and in a jaw carrier 64 to which each of a jaw 63 is attached by screw. A T-shaped projection member 65, 69 engages the T-slot 68, 70.
A face plate 71 is rigidly attached to the front end of the first body part 61 and covers the front of the chuck and has a series of work-engaging buttons 72 which engages an end face of a work-piece, as for example a pipe member 73.
As a result of the T-slot construction between the jaw carriers 64 and the plug 67, the jaw 63 will thus move axially inwardly until the work piece engages the stop buttons 72 provided on the face plate 71.
A clamping process of this construction is as follows. A rearward axial movement of the draw bar 66 by an air cylinder 74 and of the plug 67 will be accompanied by inward radial movement of the jaw carriers 64 relative to the outer body part 61 via the T-shaped projection member 65 in the T-slot 68.
As the inner body part 62 moves relative to the outer body part 61, a rear end face of the inner body part 62 abuts a spring 75 and compresses it. As a combination of the resistant force of the spring 75, T-shaped projection member 65 and the inclined T-slot 68 of the plug 67, jaw carriers 64 and the jaw 63 will thus move radially and inwardly to clamp the work piece.
Further rearward movement of the plug 67 causes rearward movement of the jaw carrier 64 and the inner body part 62, until the end face of a work-piece 73 engages the stop buttons 72. Then the axial movement of the jaw 63 is stopped and further pulling force by the air cylinder 74 is converted to a greater force to chuck the work piece tightly.
As described above, the conventional chuck construction consists of two main parts, the outer body part 61 which is secured to a spindle, and the inner body part 62 which is a movable part inside the outer body part. Consequently the whole body construction becomes big in its dimensions and the movable member causes an unstable condition when the chuck body rotates at a high speed.
Further, as the clamping force increases, a moment in the jaw carrier 64 also increases, which is bourne only by the T-slot 70 of the inner body part 62 and the T-shaped projection member 65 of the jaw carrier 64, the whole chuck body must be designed big in its dimensions to provide a durable rigidity to the chuck body.
The invention has been developed to solve the drawbacks of the conventional chuck construction, and it is an object of the invention to provide a compact chuck construction, by omitting the axial movement parts, which are inevitable in the conventional chuck construction.